Nazis thought that killing Jewish people, Roma, and other groups would

Nazis thought that killing Jewish people, Roma, and other groups would be beneficial to the German people and all mankind.

Purify the race.

Explanation:

Nazis had the Nietzsche philosophy of the Super Man, who have the power over his own feelings. This idea was misrepresented by the Nazis to justify their xenophobia against Jewish people. They believe that a Super Man could exist only from their race, they even did experiment with Jewish people to see if they could change biological characteristic into theirs.